Field of the Invention
The present invention relates to an RF coil system for use in a magnetic resonance imaging apparatus for obtaining morphological information, such as cross-sectional NMR images, and functional information, such as spectroscopy, from a subject under examination (organism) by utilizing nuclear magnetic resonance (NMR) phenomena.
RF coil systems for use in a magnetic resonance imaging apparatus and adapted for transmission of an excitation pulse and/or reception of magnetic resonance signals include a whole-body coil which is embedded in a gantry beforehand and a coil which is not embedded in the gantry beforehand. In general, the former is adapted for transmission and reception, while the latter is adapted for reception only. For the latter a surface coil is frequently used. The surface coil permits high-sensitivity reception of signals from a local region. The surface coil consists of a conductor formed in the shape of a circle or square with a diameter of ten centimeters to tens of centimeters and can receive magnetic resonance signals induced in a body portion on which it is placed at high sensitivity. Such a surface coil permits high-resolution imaging of a body portion such as a joint or the spinal column. This is very advantageous clinically.
However, every time a body portion for imaging is changed, the position of the surface coil has also to be changed. This is troublesome. That is, a subject under examination is placed on a top board with the surface coil placed between the subject and the top board or on the subject and entered into the gantry for NMR imaging. For imaging of another body portion of the subject the top board is drawn from the gantry to release the subject and position the surface coil on another body portion of the subject and the top board is entered into the gantry again. Namely, the position of the surface coil has to be changed every time a change is made from an imaging portion to another. Therefore, problems arise in that the NMR imaging time takes a long time and, in addition, the positioning of the surface coils is time-consuming.